According to the known prior art, IOLs are selected and adapted on the basis of measured and/or estimated variables, with only individual parameters being considered in the form of individual measured values or as a mean value over defined patient groups.
The selection or adaptation of the optimal intraocular lens (IOL) is done exclusively according to their characteristics, such as type, refractive power, asphericity and multifocality.
The selection of the appropriate intraocular lens (IOL) for a patient is the responsibility of the cataract surgeon. In making this selection, the surgeon must consider many factors. For one, the appropriate method for calculating the IOL dioptric power must be selected as a function of the individual biometric parameters of the eye. To this end, for unusually long, normal or unusually short eyes, various more or less appropriate formulas can generally be used for the calculation. In the simplest of cases, their input parameters are based on keratometry and the axial length of the eye, the formulas usually also containing, due to their simplified modeling assumptions, an empirically determined correction factor, such as the so-called A-constant, for example.
The method of calculation that is currently most widely used are so-called IOL formulas, for example according to Holladay, Hoffer, Binkhorst, Colenbrander, Shammas, or SRK. According to those, the refraction D (output/assessment parameter) of the patient after inserting the IOL is calculated as follows:D=DIOL−f(K,AL,VKT,A)  (1)where                f( ) is a standard, known IOL formula and        DIOL is the refractive power of the IOL,        K is the measured keratometry value,        AL is the measured axial length of the eye,        VKT is the measured anterior chamber depth, and        A is an IOL-type-dependent constant constituting the input variables.        
The constant A in the formulas is determined empirically over a patient cohort in order to adapt the expression values to the actual resulting optimal refraction values. However, the adaptation only ensures that the mean of the refraction values matches with the formula over the test cohort.
These methods of calculation are based on a paraxial approach, that is, on first-order optics. In this simplification of geometrical optics, only those light beams are observed that do not form an angle with the optical axis and are at short distances from it, thus resulting in linear formulas for calculating the light beams passing through the system. Besides chromatic aberration, paraxial beams cannot cause imaging errors; that is, such errors can be ruled out when using monochromatic light itself.